Such pressure sensors are used in many applications in the technology of pressure measurements, in order to measure the pressure of process media, which can be present in the form of liquids, gases or vapors. Essentially, such pressure sensors include a pressure measurement cell composed of a platform and an elastic membrane, or diaphragm, especially a ceramic platform and a ceramic membrane. A shallow recess is provided on the platform. This recess is referred to as the membrane bed. It is spanned by the membrane. During measurement, the membrane is loaded with the pressure of the process medium, and the deformation of the elastic membrane, which is registered, for example capacitively, or resistively, is a measure of the pressure. A corresponding pressure measurement cell is disclosed, for instance, in German Offenlegungsschrift DE 39 01 492.
During the taking of measurements, a pressure measurement cell is typically clamped between a media-side, elastic, sealing ring, which rests on the membrane-containing, end face of the sensor, and a support ring, which axially supports the membrane-far end surface of the platform, such as is illustrated, for example, in the German Offenlegungsschrift DE 42 13 857.
In so far as the deformation of the membrane depends, at given pressure, on the effective stiffness of the membrane, it is necessary to keep the membrane stiffness as constant as possible after calibration of the pressure sensor over the measuring range. It is, therefore, especially important that as few radial forces as possible act on the pressure measuring cell, since radially inwardly acting forces can decrease the membrane stiffness, and radially outwardly acting forces can increase the membrane stiffness.
Previous efforts for decreasing the influence of radial forces concerned, above all, de-coupling the rear-side friction. For this purpose, for example in the case of capacitive pressure sensors, which are manufactured and sold by the assignee under the name Cerabar, a polymer film is arranged between the rear, end face of the platform and the support ring. Additionally, the axial bearing pressure of the media-side, elastic sealing ring is reduced as much as possible, in order to minimize the introduction of lateral forces due to frictional locking. These measures have, it is true, already led to an improvement of measurement accuracy; however, a further reduction of disturbing radial forces seems desirable.